Handcuffs are well known. Such devices are typically used by police and military to at least partially restrain people being held in custody.
A pair of handcuffs are constructed of first and second handcuffs connected by a chain. Each handcuff typically includes a bow and frame. The bow is curved to fit around the wrist of a prisoner. One end of the bow is attached to and pivots on the frame. The other end of the bow has a series of sloped teeth that engage a spring-loaded pawl within the frame. A key engages a lock within the frame in order to release the handcuffs from the wrists of a prisoner.
Because of the nature of use, handcuffs must be particularly robust. As such, at least the bow, the frame and most parts of the lock are constructed of metal.
Also because of the nature of use, handcuffs must be difficult to defeat. This is typically accomplished via close tolerances in the construction of the lock and between the bow and frame to resist release of the handcuff via insertion of a metal strip between the spring-loaded pawl and bow. Because of the materials needed for robustness and the tolerances need to defeat tampering, most handcuffs are expensive to produce.
Plastic restraint devices have been proposed as an alternative to handcuffs. However, the plastic locking mechanism of such devices has been found to be subject to damage when used with particularly strong prisoners. Accordingly, a need exists for better methods of producing such devices.